Technical Field
The present invention relates to an ink jet head and a liquid jet recording apparatus.
Related Art
A liquid jet recording apparatus, for example, an ink jet printer which performs various kinds of printing operations is typically provided with a conveyance device which conveys a recording medium and an ink jet head. The ink jet head used in the ink jet printer performs recording in such a manner that ink is supplied to the ink jet head from an ink tank through an ink supply tube, and the ink is ejected onto a recording medium through a nozzle hole of a head chip disposed on the ink jet head.
The above head chip is provided with a nozzle plate which includes a nozzle array consisting of a plurality of nozzle holes and an actuator plate which is joined to the nozzle plate and includes a plurality of channels communicating with the nozzle holes. The actuator plate is filled with ink.
Further, electrodes are formed on walls which define the channels of the actuator plate. The walls are deformed by applying voltage to the electrodes, which produces pressure fluctuation in ink inside the channels. Accordingly, the ink is ejected through the nozzle holes of the nozzle plate.
A protection plate may be disposed on an ink ejection face of the nozzle plate to protect the ejection face of the nozzle plate or reduce thermal deformation of the nozzle holes. The protection plate is formed of a metal plate to ensure stiffness. Thus, the protection plate may be charged, for example, by rubbing against a recording medium. The charge of the protection plate affects the ink ejection characteristics, for example, changes the ejection direction of ink droplets.
Thus, a technique is known that uses a nozzle plate formed of silicon, provides a conductive terminal on the surface of the nozzle plate, and grounds the conductive terminal on a housing. Further, since the nozzle plate is formed of silicon in this technique, the surface of the nozzle plate is coated with a liquid droplet protection film to prevent erosion of the nozzle plate caused by ink (refer to JP 2010-143106 A, for example).
Further, a technique is known that provides a conductive portion which penetrates a nozzle plate in the thickness direction at a position facing an ink chamber (common ink chamber) and provides a conductive cover portion on the nozzle plate at a side opposite to the ink chamber. The conductive cover portion is in contact with the conductive portion and also in contact with a housing. Accordingly, the nozzle plate can be grounded through the conductive portion and the conductive cover portion (refer to JP 2011-143573 A, for example).
However, in JP 2010-143106 A, it is necessary to route the conductive terminal to connect the conductive terminal to the housing. Thus, steps of forming the conductive terminal become complicated. Further, since the nozzle plate is formed of silicon, the liquid droplet protection film is required to prevent erosion of the silicon caused by ink. Thus, the number of steps and the manufacturing cost for manufacturing the nozzle plate disadvantageously increase.
In JP 2011-143573, the conductive portion is exposed also in the ink chamber. Thus, electricity flows through ink and a short circuit occurs when the actuator plate is driven. Accordingly, the operation of the ink jet head disadvantageously becomes unstable.
Further, it is necessary to provide the conductive cover portion to ground the conductive portion. Thus, disadvantageously, the number of components increases, and the size of the ink jet head increases.